U.S. patent application number 10/041870 was filed with the patent office on 2002-07-11 for method and device for mounting cell.
This patent application is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Daio, Fumio, Sano, Akihiro, Yoshida, Daisuke.
Application Number | 20020090537 10/041870 |
Document ID | / |
Family ID | 27321468 |
Filed Date | 2002-07-11 |
United States Patent
Application |
20020090537 |
Kind Code |
A1 |
Sano, Akihiro ; et
al. |
July 11, 2002 |
Method and device for mounting cell
Abstract
A battery cell 10 is attached in an apparatus loaded in a
revolving body, etc., such that the negative electrode 2 side of
the battery cell 10 is oriented, within a prescribed angular range,
in the direction in which centrifugal force acts.
Inventors: |
Sano, Akihiro;
(Neyagawa-shi, JP) ; Daio, Fumio;
(Kitakatsuragi-gun, JP) ; Yoshida, Daisuke;
(Moriguchi-shi, JP) |
Correspondence
Address: |
JORDAN AND HAMBURG LLP
122 EAST 42ND STREET
SUITE 4000
NEW YORK
NY
10168
US
|
Assignee: |
Matsushita Electric Industrial Co.,
Ltd.
Kadoma-shi
JP
|
Family ID: |
27321468 |
Appl. No.: |
10/041870 |
Filed: |
October 25, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10041870 |
Oct 25, 2001 |
|
|
|
09212964 |
Dec 16, 1998 |
|
|
|
Current U.S.
Class: |
429/1 ; 29/623.1;
429/100 |
Current CPC
Class: |
H01M 50/216 20210101;
Y02E 60/10 20130101; Y10T 29/53135 20150115; H01M 10/425 20130101;
Y10T 29/49108 20150115; H01M 6/16 20130101 |
Class at
Publication: |
429/1 ; 429/100;
29/623.1 |
International
Class: |
H01M 002/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 1997 |
JP |
9-353297 |
Jun 8, 1998 |
JP |
10-159077 |
Nov 4, 1998 |
JP |
10-312903 |
Claims
What is claimed is:
1. A battery cell attachment method wherein: when a battery cell,
wherein positive polarity material and negative polarity material
are placed in opposition through a separator in a battery case, and
a liquid electrolyte is packed into said battery case, is attached
in an apparatus installed in a place acted on by centrifugal force,
said battery cell is attached in said apparatus so that one side
where the negative polarity material is present faces in a
direction in which said centrifugal force is acting on said
apparatus.
2. The battery cell attachment method according to claim 1,
wherein, when said battery cell of which battery case is a flat
shape is divided in two in the thickness direction thereof, and
vacant volume remaining after volumes of negative polarity
material, positive polarity material, and separator are subtracted
from volume inside said battery case in each divided part said
battery cell is attached such that said vacant volume is smaller in
said divided part on side where negative polarity material is
placed than in said other divided part.
3. The battery cell used in the attachment method according to
claim 1, configured by placing a positive polarity material of
which main component is either a metal oxide, halide, or sulfide,
and a negative polarity material of which main component is either
light metal or light metal alloy, so that they oppose each other
through a separator made of a substance capable of withstanding
temperatures in excess of 150.degree. C., into a battery case:
packing a liquid electrolyte consisting of an organic solvent or
mixture of organic solvents having a solvent boiling point of
170.degree. C. or higher into which a lithium salt is dissolved as
a solute between the positive polarity material and the negative
polarity material; and sealing the opening in said battery case
with a sealing plate, with an intervening gasket that is resistant
to temperatures in excess of 150.degree. C. and resistant also to
organic solvents.
4. The battery cell of claim 3, wherein said separator is made of a
substance selected from among glass fiber, polyphenylene sulfide
fiber, vinylidine polyfluoride resin, polytetrafluoroethylene
resin, polybutylene terephthalate resin, and ceramic resin.
5. The battery cell of claim 3, wherein said organic solvent is
made of a substance selected from among gamma butylolactone,
ethylene carbonate, butylene carbonate, propylene carbonate,
sulfolane, and 3-methyl sulfolane.
6. The battery cell of claim 3, wherein said gasket is made of a
substance selected from among polyphenylene sulfide resin polyether
ketone resin, polyether ether ketone resin polytetrafluoroethylene
resin and vinylidene tetrafluoride resin.
7. A battery cell attachment method wherein: when a battery cell
wherein a positive polarity material and a negative polarity
material are placed in opposition in a battery case with an
intervening separator and wherein a liquid electrolyte is packed
inside said battery case, is attached in an apparatus installed in
a place acted on by centrifugal force, said battery cell is mounted
in said apparatus so that negative polarity material side of said
battery cell faces in direction in which said centrifugal force
acts on said apparatus, and angle of inclination of thickness
direction of said battery cell is within a range of 0 to 60 degrees
relative to direction of said centrifugal force.
8. The battery cell attachment method according to claim 7,
wherein, when said battery cell of which said battery case is a
flat shape is divided in two in thickness direction thereof, and
vacant volume remaining after volumes of negative polarity
material, positive polarity material, and separator are subtracted
from volume inside said battery case in each divided part is
calculated, said battery cell is attached such that said vacant
volume is smaller in said divided part on side where negative
polarity material is placed than in said other divided part.
9. The battery cell used in the attachment method according to
claim 7, configured by placing a positive polarity material of
which main component is either a metal oxide, halide, or sulfide,
and a negative polarity material of which main component is either
light metal or light metal alloy, so that they oppose each other
through a separator made of a substance capable of withstanding
temperatures in excess of 150.degree. C., into a battery case;
packing a liquid electrolyte consisting of an organic solvent or
mixture of organic solvents having a solvent boiling point of
170.degree. C. or higher into which a lithium salt is dissolved as
a solute between the positive polarity material and the negative
polarity material; and sealing the opening in said battery case
with a sealing plate, with an intervening gasket that is resistant
to temperatures in excess of 150.degree. C. and resistant also to
organic solvents.
10. The battery cell of claim 9, wherein said separator is made of
a substance selected from among glass fiber, polyphenylene sulfide
fiber, vinylidine polyfluoride resin, polytetrafluoroethylene
resin, polybutylene terephthalate resin, and ceramic resin.
11. The battery cell of claim 9, wherein said organic solvent is
made of a substance selected from among gamma butylolactone,
ethylene carbonate, butylene carbonate, propylene carbonate,
sulfolane, and 3-methyl sulfolane.
12. The battery cell of claim 9, wherein said gasket is made of a
substance selected from among polyphenylene sulfide resin,
polyether ketone resin, polyether ether ketone resin,
polytetrafluoroethylene resin, and vinylidene tetrafluoride
resin.
13. A battery cell attachment device wherein: when a battery cell
wherein a positive polarity material and a negative polarity
material are placed in opposition in a battery case with an
intervening separator, and wherein a liquid electrolyte is packed
inside said battery case, is attached in an apparatus installed in
a place acted on by centrifugal force, said battery cell is mounted
in a prescribed position in said apparatus, using attachment means
for making negative polarity material side of said battery cell
face in direction in which said centrifugal force acts on said
apparatus, and regulating battery cell installation direction so
that angle of inclination of thickness direction of said battery
cell relative to said direction of centrifugal force is within a
prescribed range.
14. The battery cell attachment device of claim 13, wherein the
attachment means has an attachment structure configured such that
only one of the positive polarity side and negative polarity side
of the battery cell having mutually different outer shapes fits in
this attachment means, whereby said battery cell can be loaded in
such manner that battery cell installation direction is regulated.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an attachment method and
attachment device for battery cells installed in locations
subjected to centrifugal forces.
[0003] 2. Description of the Related Art
[0004] Apparatuses which use battery cells as power supplies are
not limited to portable equipment, and various utilization
configurations are now being developed. Among these applications
are automobiles, space observation equipment, and various types of
industrial equipment wherewith battery cells need to be used in
environments affected by centrifugal forces. In battery cell
applications in apparatuses designed for measuring and monitoring
air pressure of an automobile tire while the vehicle is moving, for
example, the centrifugal force developed by tire revolution acts on
the battery cells. The conditions affecting such battery cells when
subjected to centrifugal forces are now described.
[0005] The chemical reactions that take place in battery cells are
based on ion conduction in liquid electrolytes that are present
between a positive polarity material and a negative polarity
material. In general, liquid electrolytes are present in a
condition wherein they are impregnated in separators placed between
the positive polarity material and the negative polarity material,
in which condition they contribute to oxidation-reduction reactions
between positive and negative electrodes. More specifically, if the
active material of positive electrode (positive polarity material)
is designated P1, and the active material of negative electrode
(negative polarity material) is designated N1, then the reaction
that proceeds at the positive pole is represented by chemical
equation (1), and the reaction that proceeds at the negative pole
is represented by chemical equation (2).
[0006] (1) Positive Pole: P1+ne.sup.-.fwdarw.P2
[0007] (2) Negative Pole: N1.fwdarw.N2+ne.sup.-
[0008] When the reactions expressed by the chemical equations (1)
and (2) come into contact via the liquid electrolyte, a DC current
can be sent to a circuit connected to the battery cell, whereupon
the electricity generating reactions of the battery cell proceed.
When such battery cell reactions as these are subjected to
centrifugal forces, due to electrolyte flow induced by the
centrifugal forces, the electrolyte available for contributing to
the electricity generating reactions sometimes decreases, resulting
in a decline in battery cell performance. This is now described in
the case of a graphite-lithium fluoride battery cell, which is one
example of a non-aqueous liquid electrolyte battery cell.
[0009] In the graphite-lithium fluoride battery cell, as diagrammed
in FIG. 1, a negative electrode 2 formed as a disk made from
lithium metal and a positive electrode 3 formed as a disk made from
a material of which main component is graphite fluoride are stacked
in a battery case 5 made of stainless steel, separated by a
separator 4 formed of unwoven polypropylene fabric. The interior of
this battery case is filled with a liquid electrolyte wherein
lithium borofluoride is dissolved in a liquid mixture of dimethoxy
ethane (DME) having a low boiling point and either gamma
butyrolactone or propylene carbonate having a high boiling point to
bring the volumetric concentration thereof to 1 mol/liter. The
opening in the battery case 5 is sealed by a sealing plate 1 made
of stainless steel that doubles as a negative terminal, with an
intervening gasket 6 formed of a polypropylene resin.
[0010] When a centrifugal force acts in the thickness direction on
a flat battery cell such as this, an electrolyte that exhibits
mobility will move in the direction of the centrifugal force toward
one or other of the electrodes, whereupon the volume of electrolyte
available for contributing to the electricity generating reactions
of the battery cell at the other electrode will decrease. This
results in a decline in such battery performance factors as
discharge capacity and discharge characteristics, as compared to
when the battery cell is used in a normal condition unaffected by
centrifugal forces.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a battery
cell attachment method and attachment device for battery cell
applications in environments subjected to centrifugal forces,
wherewith battery cell performance does not decline.
[0012] What is characteristic of the battery cell attachment method
of the present invention is that, when a battery cell wherein
positive polarity material and negative polarity material are
placed in opposition through a separator or separators in a battery
case, and a liquid electrolyte is packed between the positive
polarity material and the negative polarity material, is attached
in an apparatus installed in a place acted on by centrifugal
forces, the battery cell is attached in the apparatus so that one
side where the negative polarity material exists faces in a
direction in which the centrifugal force is acting on the
apparatus. By attaching the battery cell so that the negative
polarity material faces in the direction of centrifugal force in
this manner, a condition is maintained wherein the liquid
electrolyte that flows due to the centrifugal force is present on
the opposite side of the negative polarity material that becomes
the depolarized side during discharge, and battery cell performance
deterioration due to centrifugal force is prevented.
[0013] What is further characteristic of the battery cell
attachment method of the present invention is that, when a battery
cell wherein positive polarity material and negative polarity
material are placed in opposition through a separator or separators
in a battery case, and a liquid electrolyte is packed between the
positive polarity material and the negative polarity material, is
attached in an apparatus installed in a place acted on by
centrifugal forces; the battery cell is attached in the apparatus
so that the negative polarity material side is oriented with
respect to the direction in which the centrifugal force acts on the
apparatus so that the angle of inclination of the battery cell
thickness direction is within a range of 0 to 60 degrees. The
liquid electrolyte present at the reaction surface of the negative
polarity material decreases the more as the inclination of the
thickness direction increases from the attachment angle in a
battery cell wherein the negative polarity material is oriented in
the direction of the centrifugal force. However, if that angle of
inclination is within 60 degrees, so long as a condition wherein
excessive centrifugal forces act is avoided, the apparatus can be
operated in a condition that is not problematic in practice,
without suffering any extreme decline in the discharge
capacity.
[0014] With the attachment method noted in the foregoing, when a
battery cell wherein the battery case is formed as a flat shape is
divided into two in the thickness direction, and the vacant
capacity left after subtracting the volume occupied by the negative
polarity material, the positive polarity material, and the
separator from the volume in the battery case, in each of the
divided portions, is computed, the vacant capacity of the divided
portion on the side where the negative polarity material is located
is smaller than that of the divided portion on the other side, and
it is possible to attach the battery cell with this side having the
smaller vacant capacity oriented in the direction of the
centrifugal force. The decline in battery performance due to
centrifugal forces acting on the battery cell results when liquid
electrolyte is not sufficiently present at the surface of the
negative polarity material during the course of electricity
generating reactions. Accordingly, when the negative polarity
material is on the side of the battery cell having the smaller
vacant capacity, and the battery cell is attached so that this side
is in the direction of the centrifugal force, a condition is
maintained wherein the liquid electrolyte is present at the surface
of the negative polarity material, wherefore the decline in battery
performance due to centrifugal force is checked.
[0015] The battery cell attachment method of the present invention
is a method for attaching a battery cell wherein positive polarity
material and negative polarity material are placed in opposition
through a separator in a battery case, and that battery case is
packed with a liquid electrolyte, in an apparatus installed in a
place acted on by centrifugal forces, wherein the negative polarity
material side of the battery cell is oriented toward the direction
in which centrifugal force acts on the apparatus, and the battery
cell is loaded in a prescribed position in the apparatus using
attachment means that regulate the battery cell loading direction
so that the angle of inclination of the battery cell thickness
direction relative to the centrifugal force direction is within a
prescribed range. Thus the negative polarity material side of the
battery cell is regulated so that it is oriented with respect to
the direction of centrifugal force within a prescribed angular
range, a state is obtained wherein the liquid electrolyte is
sufficiently present when centrifugal force acts on the reaction
surface of the negative polarity material, and the battery cell can
be attached in a condition wherein battery performance does not
decline due to centrifugal force.
[0016] The attachment means noted above are configured so that the
battery cell can be loaded in such manner that the loading
direction is regulated by a battery cell attachment structure
wherein, of the positive-polarity side and negative polarity side
having mutually different outer shapes, only the shape on the side
of one pole fits.
[0017] The battery cell used in the attachment method and
attachment device noted in the foregoing is made by placing a
positive polarity material formed primarily of either a metal
oxide, halide, or sulfide, and a negative polarity material made
primarily of either light metal or light metal alloy, so that they
oppose each other through a separator made of a substance capable
of withstanding temperatures in excess of 150.degree. C., into a
battery case that functions also as the positive terminal; packing
a liquid electrolyte consisting of an organic solvent having a
boiling point of 170.degree. C. or higher into which is dissolved a
solute, in which a lithium salt is used, between the positive
polarity material and the negative polarity material; and sealing
the opening in the battery case with a sealing plate that also
functions as the negative terminal, with an intervening gasket that
is resistant to organic solvents and resistant to temperatures in
excess of 150.degree. C. Thus, by forming the separator gasket, and
liquid electrolyte of materials capable of withstanding high
temperatures, vaporization of the liquid electrolyte by high
temperature is suppressed, and deterioration in the separator and
gasket due to high temperature is prevented. Simultaneous exposure
to high temperatures often occurs in environments acted on by
centrifugal forces, wherefore battery cells having a heat-resistant
structure are effective.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a cross-sectional view showing the configuration
of a battery cell in an embodiment of the present invention;
[0019] FIG. 2 is a plan view showing the configuration of a battery
cell attachment device in the same embodiment;
[0020] FIG. 3 is a cross-sectional view in the III-III plane
indicated in FIG. 2; and
[0021] FIG. 4 is a cross-sectional view showing the configuration
of a battery cell in an embodiment of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] Embodiments of the present invention are now described, with
reference to the attached drawings.
[0023] The electricity generating elements of the battery cell are
configured as the three basic elements of positive polarity
material, negative polarity material, and liquid electrolyte. FIG.
1 shows an example of a graphite-lithium fluoride battery cell,
which is formed in a flat shape and commonly called a button
battery. A positive electrode 3 and negative electrode 2
configuring the electricity generating elements are stacked
together with an intervening separator 4, and placed inside a
battery case 5. The positive electrode 3 is formed as a disk that
is made of a material of which main component is graphite fluoride,
while the negative electrode 2 is formed as a disk made of lithium
metal. The separator 4 is formed of a polypropylene unwoven fabric.
This battery case 5 is filled with a liquid electrolyte that is
obtained by dissolving a lithium salt as the solute into an organic
solvent, thereby configuring the electricity generating elements as
a graphite-lithium fluoride battery cell. Thereafter, the opening
of the battery case 5 is sealed with a sealing plate 1. When
effecting this seal, a gasket 6 is placed between the battery case
5 and the sealing plate 1 in order both to insulate the battery
case 5 and the sealing plate 1 from each other and to enhance the
airtight condition inside the battery case 5.
[0024] When such a battery case as this is used in a condition
wherein it is acted on by a centrifugal force, it sometimes happens
that the configurational balance between the electricity generating
elements is destroyed by the flowing of the liquid electrolyte in
the direction of the centrifugal force, leading to a decline in
battery cell performance. Such conditions arise, for example, in
applications wherein the battery cell is used as a power source in
an apparatus installed in a revolving body such as an automobile
tire in order to measure and monitor air pressure in the tire. The
liquid electrolyte is interposed between the positive electrode 3
and the negative electrode 2 and contributes to the electrochemical
reaction between the positive and negative electrodes. When this
liquid electrolyte flows in the direction of the centrifugal force
so that it favors one direction, the possibility that the
electrochemical reaction cannot proceed normally arises.
[0025] Embodiments of a battery cell attachment method and
attachment device for suppressing deterioration in battery cell
performance caused by such centrifugal forces are now
described.
[0026] In order to verify changes in battery cell performance due
to centrifugal forces, battery cells were loaded and rotated in a
revolving test machine, and the changes in discharge capacity
caused by the centrifugal force of revolution were measured. The
battery cells subjected to this test were the flat graphite-lithium
fluoride battery cells (model symbol BR2330) diagrammed in FIG. 1
having an outer diameter of 23 mm and outer thickness of mm. The
discharge capacity of these battery cells was measured with a low
resistance discharge of 15 k.OMEGA. at a room temperature of
25.degree. C.
[0027] Taking a discharge capacity of 255 mAh, in a condition where
no centrifugal force is acting, as a discharge capacity utilization
factor of 100%, the way in which this changed, according to the
strength of the centrifugal force and the battery cell attachment
angle, was measured. Verification of the discharge capacity was
based on measurements of times required to arrive at a final
discharge voltage of 2.0 V. Taking battery cell variation into
consideration, this was calculated in terms of the mean value for
20 test cells. The ratio of battery space volume occupied by the
liquid electrolyte in the battery cells used in this test was 42
vol %.
[0028] The results of the measurements made of discharge capacity
(battery cell capacity) utilization rates according to the
centrifugal force and the battery cell attachment angle under these
measurement conditions are listed in Table 1. The angle of battery
cell attachment relative to the direction of centrifugal force is
assumed to be 0 degrees at the angle where the center axial
direction from the center of the positive electrode 3 toward the
center of the negative electrode 2 coincides with the centrifugal
force direction, that is, at the angle where the plate face of the
negative electrode 2 faces in the same direction as the centrifugal
force, as diagrammed in FIG. 1. This angle is assumed to be 180
degrees when this is inverted and the plate face of the positive
electrode 3 faces in the same direction as the centrifugal force.
The changes in discharge capacity were measured at all the angles
between 0 degrees and 180 degrees, for each of various strengths of
centrifugal force.
1TABLE 1 Battery cell capacity utilization factor (%) according to
centrifugal force and battery cell attachment angle Angle of
inclination of battery cell thickness direction to Centrifugal
centrifugal force direction force 0.degree. 20.degree. 45.degree.
60.degree. 90.degree. 120.degree. 135.degree. 180.degree. 1 G 100
100 100 100 100 100 100 100 30 G 100 100 100 100 100 100 99 98 50 G
100 99 97 94 55 48 41 32 80 G 100 95 92 90 46 37 23 11 150 G 100 91
88 85 43 31 19 9 500 G 100 89 82 77 39 29 17 5 1000 G 100 87 75 71
36 24 13 2
[0029] As can be seen from the measurement results noted in Table
1, when the battery cell attachment angle is 90 degrees or greater,
a large decline in discharge capacity is observed under centrifugal
forces exceeding 50 G. resulting in conditions wherein normal
battery cell performance cannot be realized. Accordingly, when the
centrifugal force becomes large, a decline in discharge capacity
will occur at any attachment angle other than 0 degrees. Therefore,
when loading the battery cell into an apparatus affected by
centrifugal forces, it is necessary to attach it so that the
negative plate face is oriented toward the direction of centrifugal
force. When the attachment angle is less than 60 degrees, however,
there is no excessive decline in the discharge capacity so long as
no large centrifugal force is applied. Hence, in an apparatus such
as that for measuring air pressure in automobile tires, mentioned
earlier, there will be little problem in practice so long as the
battery cell is installed with an attachment angle of 60 degrees or
less.
[0030] This decline in discharge capacity due to the application of
centrifugal force is believed to be caused by a condition
developing wherein liquid electrolyte necessary for discharge at
the negative electrode that is the depolarized surface during
discharge is not adequately present. This condition develops
conspicuously in flat battery cells wherein a positive electrode
and negative electrode are placed in parallel opposed to each
other. Accordingly, it becomes possible to obtain normal operation
even in conditions wherein centrifugal forces are acting by
applying the attachment method described above not only to the
graphite-lithium fluoride battery cells described but also to other
types formed as buttons or paper forms.
[0031] The inventors also verified that, so long as the ratio
whereby the liquid electrolyte occupies the battery cell space
volume is within a range of 20 to 70 vol %, similar effects can be
realized irrespective of the type of liquid electrolyte
employed.
[0032] An attachment device for mounting a battery cell at the
attachment angle noted above is now described.
[0033] In FIG. 2 is shown the configuration of an attachment device
30 for attaching a battery cell 10 in a circuit board 12 in an
apparatus wherein the battery cell 10 is used as the power supply.
The external shape of the battery cell 10 formed as a flat disk, as
diagrammed in FIG. 1, wherein the radius of the circumferential
corners are different on the negative electrode side and the
positive electrode side, wherefore the attachment device 30 is
formed with an inner surface shape corresponding to the shape of
the negative electrode side of the battery cell 10, so that the
battery cell 10 cannot be installed with the positive and negative
orientations reversed. Accordingly, when this attachment device 30
is used in attaching the battery cell 10 to the circuit board 12,
the attachment will always be made so that the negative electrode
side of the battery cell 10 is oriented in a fixed direction.
[0034] As shown in FIG. 3, the attachment device 30 configuration
comprises a positive electrode plate 11 that is in contact with the
battery case 5 connected to the positive electrode 3 (cf. FIG. 1)
of the battery cell 10, an attachment bracket 8 that is in contact
with the sealing plate 1 connected to the negative electrode 2 of
the battery cell 10, and an insulating cover 9 between the
attachment bracket 8 and the battery case 5. The positive electrode
plate 11, in addition to having the positive terminal 11b thereof
soldered to a plus power supply line in the circuit pattern formed
on the circuit board 12, is secured by an adhesive or the like onto
the circuit board 12. A ring-shaped positive electrode contact
projection 11a is formed in the part where the battery cell 10 is
mounted thereby effecting a stably conducting contact with the
battery case 5 of the battery cell 10. The insulating cover 9 is
formed by resin molding. In the middle thereof is formed an opening
9a for accommodating the sealing plate 1 of the battery cell 10.
The inner surface shape thereof is formed so as to coincide with
the radius shape on the negative electrode side of the battery case
5 and so as to fit into the negative electrode side of the battery
cell 10. The attachment bracket 8 is formed, moreover, in a shape
that covers the insulating cover 9. A conducting contact is
effected with the sealing plate 1 inserted inside the opening 9a in
the insulating cover 9 by a negative electrode contact projection
8a formed in the middle thereof. Attachment pieces 8b are formed at
three locations about the periphery of the attachment bracket 8. By
screwing the attachment bracket 8 down to the circuit board 12
using screw holes 8c, the battery cell 10 is securely mounted on
the circuit board 12, and the negative electrode of the battery
cell 10 is connected to a minus line in the circuit pattern formed
on the circuit board 12.
[0035] This circuit board 12 is attached so that the attachment
surface side of the battery cell 10 faces in the direction of the
centrifugal force acting on the apparatus that is configured using
the circuit board 12, whereby the negative electrode side of the
battery cell 10 is oriented in the direction of the centrifugal
force. That being so, battery cell performance is prevented from
declining due to liquid electrolyte flow resulting from the
centrifugal force, as described earlier. The battery cell 10 is
held securely to the circuit board 12 by the attachment bracket 8,
moreover, wherefore it can be prevented from being separated from
the circuit board 12 by centrifugal force. Furthermore, even in
cases where the negative electrode side of the battery cell 10
cannot be made to face in the direction of the centrifugal force,
by making the attachment so that the negative electrode side is
oriented so that it is within an angular range of at least 60
degrees with the direction of the centrifugal force, there will be
no excessive decline in the discharge capacity, and the battery
cell 10 can be used in a condition that presents no problems in
practice.
[0036] As described in the foregoing, as based on the battery cell
attachment method and device in this embodiment, the angle at which
a battery cell is attached when mounted in an apparatus acted on by
centrifugal forces is regulated, whereby the development of a
condition wherein the liquid electrolyte is decreased at the
negative electrode reaction surface by centrifugal force is
suppressed, so that the battery cell can be operated normally even
when acted on by centrifugal forces.
[0037] A battery cell attachment method that suppresses the decline
in battery cell performance caused by the action of centrifugal
forces can also be configured as described below.
[0038] In FIG. 4, a battery cell 15 is configured as a
terminal-equipped battery cell wherein a positive terminal 13 and a
negative terminal 14, respectively, are attached to the positive
and negative electrodes in the battery cell 10 in the first
embodiment. This battery cell 15 is attached to the circuit board
by the positive terminal 13 and the negative terminal 14. What is
fundamental here, however, in terms of the direction of attachment
at this time, is that, when the bare battery cell 10 (which is the
same as the battery cell 10, in the first embodiment) excluding the
positive terminal 13 and the negative terminal 14, is divided into
two in the thickness direction, as shown in the figure, the
attachment is effected so that the side on which the vacant
capacity inside the battery case 5 is smaller is oriented in the
direction of centrifugal force.
[0039] The vacant volume mentioned above is the remaining volume in
the battery cell space volume inside the battery case 5, after the
battery case 5 has been sealed by the sealing plate 1, that is not
occupied by the volume of the electricity generating elements
accommodated therein. In the case of the graphite-lithium fluoride
battery cell shown in FIG. 3 with an outer diameter of 23 mm and an
outer thickness of 3 mm, the battery cell space volume is 761
.mu.l. The volume of the fixed elements such as the positive
electrode 3, negative electrode 2, and separator 4, etc., is 369
.mu.l. The volume of the liquid electrolyte is 342 .mu.l.
Accordingly, the vacant volume is 50 .mu.l, and the ratio of the
battery cell space volume occupied by the liquid electrolyte is 45
vol %. When this battery cell 10 is divided into two in the
thickness direction, it is the negative electrode 2 side on which
the vacant volume becomes smaller. The vacant volume on this side
is 12 .mu.l. Conversely, it is the positive electrode 3 side on
which the vacant volume becomes larger. The vacant volume is 38
.mu.l on this side.
[0040] Thus, in a flat graphite-lithium fluoride battery cell, it
is the negative electrode 2 side on which the vacant volume becomes
smaller. When the battery cell is attached so that this side is
oriented in the direction of centrifugal force, within the
prescribed angular range, the effects of centrifugal force can be
suppressed.
[0041] As described in the foregoing, in cases where a battery cell
is used as the power source for an air pressure measuring and
monitoring apparatus in an automobile tire, at the same time that
centrifugal forces are acting due to the revolution of the tires,
the apparatus is subjected also to a high-temperature environment.
When, for instance, an automobile is being driven down a hill under
breaking, the temperature environment around the battery cell
reaches the high temperatures of 100.degree. C. to 150.degree. C.
When battery cells are installed in a revolving body such as a tire
like this, it often happens that, in addition to the centrifugal
forces, the effects of heat produced by friction, etc.. cannot be
avoided either.
[0042] When a conventional lithium cell is used or stored in a
high-temperature environment at 70.degree. C. or higher, or is
subjected to heat shock loads, the polypropylene resin used as the
separator and gasket material deteriorates due to heat-induced
oxidation because the temperature at which the cell can be
continuously used is approximately 65.degree. C. Deterioration in
the gasket causes gaps to develop in the seal, whereupon the liquid
electrolyte leaks out or moisture enters from the outside,
resulting in a decline in battery cell performance. In particular,
when a low-boiling point solvent like DME is used as the solvent in
the liquid electrolyte, the liquid electrolyte readily vaporizes at
temperatures above 85.degree. C. and escapes from minute gaps in
the seal.
[0043] When exposed to such high-temperature environments as this,
battery cells can be used if they have been given a heat-resistant
structure. In FIG. 3, the material adopted for the separator 4
placed between the negative electrode 2 and positive electrode 3 is
capable of withstanding temperatures in excess of 150.degree. C.
Such materials include glass fiber, polyphenylene sulfide (PPS)
resin, vinylidene polyfluoride resin, polytetrafluoroethylene,
polybutylene terephthalate (PET) resin unwoven fabric, and ceramic
fiber, etc. Suitable class fiber will have a mean fiber diameter of
2 .mu.m or less (preferably 0.3-1.5 .mu.m), a weight per unit
volume of 5.0 to 9.0 g/m.sup.2, and a mean pore diameter of 3.0 to
7.5 .mu.m. Suitable PPS fiber will have a mean fiber diameter of 30
.mu.m or less (preferably 1.0-20 .mu.m) and a weight per unit
volume of 10.0 to 100.0 g/m.sup.2. And suitable PBT fiber will have
a mean fiber diameter of 15 .mu.m or less (preferably 0.5-10
.mu.m), a weight per unit volume of 25.0 to 100.0 g/m.sup.2, and a
mean pore diameter of 10.0 to 60.0 .mu.m.
[0044] The material adopted for the gasket 6 placed at the seal
between the sealing plate 1 and the battery case 5 should be
resistant to temperatures in excess of 150.degree. C. and also be
resistant to organic solvents. Suitable materials include
polyphenylene sulfide resins, polyether ketone resins, polyether
ether ketone resins, polytetrafluoroethylene resins and vinylidene
tetrafluoride resins, etc. For the liquid electrolyte, an
electrolyte that is obtained by dissolving a lithium salt as a
solute into an organic solvent or mixture of organic solvents
having a boiling point of 170.degree. C. or higher is used. The
organic solvent or solvents used may be selected from among gamma
butylolactone, propylene carbonate, ethylene carbonate, and
butylene carbonate. In order to enhance high-temperature
reliability, moreover, the organic solvent used may be either
sulfolane or 3-methyl sulfolane, or a mixture of both, having a
boiling point above 200.degree. C.
[0045] Examples in which the materials noted above are used for the
gasket 6, separator 4, and liquid electrolyte are listed in Table 2
below as Embodiments 1-6. Heat-resistance performance was verified
by testing battery cells having the structures indicated for
Embodiments 1-6 and Comparative Examples 1-6. This was a discharge
test wherein, after storing the battery cells set at a discharge
capacity of 255 mAh for 30 days in a high-temperature environment,
they were discharged, at an ambient temperature of 20.degree. C.,
through a discharge resistance of 30 k.OMEGA., until a final
discharge voltage of 2.0 V was arrived at. The results of
measurements of discharge capacity and capacity survival rate in
these tests are noted in Table 2. Twenty samples were used for each
battery cell. The measured values represent mean values calculated
for each set of 20 samples.
[0046] In order to verify the deterioration in the battery cells
caused by heat shock, 100-cycle heat shock tests were conducted on
battery cells configured as in Embodiments 1-6 and Comparative
Examples 1-6, with each cycle including 2 hours at a low
temperature of -20.degree. C. and 2 hours at a high temperature of
80.degree. C. for a total of 4 hours. The results of these tests,
in which battery cell voltage failure rates and liquid electrolyte
leakage rates were measured, are noted in Table 2. The number of
samples used for each battery cell was 200, and the measurement
results noted are mean values calculated for each set of 200
samples.
[0047] In Table 2, moreover, polyphenylene sulfide resin is noted
as PPS, polyether ketone resin as PEK, polyether ether ketone resin
as PEEK, polypropylene resin as PP, gamma butylolactone resin as
GBL, dimethoxy ethane as DME, epoxy resin as EP, polyurethane resin
as PU, and polyethylene terephthalate as PET.
2 TABLE 2 Liquid Voltage electro- failure Leakage Discharge
Survival Gasket Separator lyte rate rate capacity rate Embodi- PPS
Glass GBL 0 0.2 185 72.5 ment 1 resin fiber Embodi- PPS PPS GBL 0 0
184 72.1 ment 2 resin fiber Embodi- PEK Glass GBL 0 0 188 73.7 ment
3 resin fiber Embodi- PEK PPS GBL 0 0 181 70.9 ment 4 resin fiber
Embodi- PEEK PPS GBL 0 0.1 182 71.3 ment 5 resin unwoven fabric
Embodi- PEEK Glass GBL 0 0 180 70.5 ment 6 resin fiber Compara- PPS
PP GBL 88 0 12 4.7 tive resin unwoven Example 1 fabric Compara- PPS
Glass GBL+ 2 0.2 0 0 tive resin fiber DME Example 2 Compara- PEK PP
GBL+ 100 0 0 0 tive resin unwoven DME Example 3 fabric Compara-
PEEK PPS GBL+ 1 0 0 0 tive resin unwoven DME Example 4 fabric
Compara- PP Glass GBL 98 100 17 6.7 tive resin fiber Example 5
Compara- PP Glass GBL + 100 100 0 0 tive resin fiber DME Example
6
[0048] As is evident from the test results noted in Table 2, in
Comparative Examples 1-6, configured conventionally, the discharge
capacity survival rate becomes zero or very small in a
high-temperature environment. In the battery cells in Embodiments
1-6, however, which employ heat-resistant materials in the
structural elements, the discharge capacity survival rate is 70% or
higher, indicating that practically allowable battery cell
performance can be maintained despite the harsh conditions.
[0049] As is also clear from the test results given in Table 2, in
Comparative Examples 1-6, configured conventionally, voltage
failures develop in the face of heat shock, and leakage developed
in 100% of the battery cells in Comparative Examples 5 and 6. In
the battery cells in Embodiments 1-6 in which heat-resistant
materials are used for the structural elements, on the other hand,
there was no occurrence of voltage failure at all, with only slight
leakage observed in the battery cells of Embodiments 1 and 5. It is
evident from these test results that, by adopting a configuration
wherewith both the voltage failure rate and leakage rate are zero,
as noted above, battery cell reliability in the face of heat shock
can be improved.
[0050] The purpose of the embodiments of the present invention
described in the foregoing is to elucidate the technical
particulars of the present invention; the embodiments are not
intended to limit the technical scope of the present invention. The
present invention may be implemented in various different
modifications within the scope set forth in the claims.
* * * * *